Earthquake Mitigation Research Program of Highway Systems

Sponsor: Federal Highway Administration (FHWA)

Co-PIs: Neil Anderson, Genda Chen, Ronaldo Luna, Shamsher Prakash, Rick Stephenson

Overview
The overall objective of this agreement is to improve earthquake resistance, and mitigate earthquake damage to highway transportation networks, including loss of bridges and highways. This can be accomplished by developing new seismic design and assessment methodologies, by improving seismic retrofitting measures, and by exchanging and transferring new technologies. To achieve this goal, seven research elements have been established. The status of these elements is described in detail as follows.

OBJECTIVES:

Element 1 - Project Administration and Reporting
To facilitate communication and provide a better understanding of the expertise/direction of project team members, monthly meetings have been held and various researchers have made presentations in their specialty areas. Such meetings will continue on a bi-monthly basis (starting in August) to provide/enhance communications between researchers. To ensure practical utility of contract deliverables, the Missouri S&T research team discussed the same with engineers from Missouri Department of Transportation (MoDOT) and FHWA Regional Office.

Element 2 - Develop/Demonstrate Loss-Estimation Methods for Highway Transportation Systems in the New Madrid Seismic Zone (NMSZ)
Several loss estimation methods are available in the literature. Their application has been limited to the highway transportation systems in the metropolitan areas, such as Memphis and Los Angeles. The main purpose of this element is to select and apply a loss estimation methodology to the existing highway transportation system of the St. Louis metropolitan area. The intent is to demonstrate the methodology developed by FHWA and other earthquake research centers to a complex highway system potentially affected by NMSZ.

Element 3 - Post-Earthquake Damage Evaluation of Bridge Structures
Visual inspection represents the current practice of most post-earthquake evaluations of bridge structural conditions. In many cases, this procedure leads to over-conservative conclusions, and decisions could be made to close a bridge when it is still capable of carrying reduced traffic loads. This procedure could also be ineffective in terms of the assessment of a damaged bridge that has been retrofitted with steel or composite jacketing on columns. For the purpose of economic emergency operations and associated life safety, a more quantitative measurement of structural conditions is needed. The purpose of this element is to develop and adopt one or more damage detection techniques applicable for post-earthquake evaluation of structural conditions

Element 4 - Study Near-Fault Earthquake Effects for Highway Bridge
In combination with vertical ground motions, long period strong motion pulses generated in the near-field area can cause significant damage to simply supported bridge spans, as observed during the 1999 Taiwan earthquake. Many highway bridges in the Central and Eastern United States were constructed in a similar manner to those observed in Taiwan. The purpose of this element is to evaluate the likely performance of simple-span bridges in the near-field zone due to near-fault energy pulses, directivity and fling effects, and to develop time history ground motions that may better characterize the non-linear response of bridges near the NMSZ.

Element 5 - Conduct Foundation and Geotechnical Studies for Earthquake Hazards Mitigation
NMSZ differs from other earthquake hazard regions in three primary ways. The earthquakes postulated for this region are expected to have higher frequency, longer duration of strong motion and longer recurrence intervals. The Mississippi Embayment area is covered with thick alluvial soil and unconsolidated sediments. Silt, silty sands and sandy silty soils are widespread in this region. The purpose of this element is to better understand the seismic behavior of the stratigraphy and geologic structure of the region and the seismic response of short-to-medium span bridges. Once seismic performance is understood, retrofitting alternatives will be investigated.

Element 6 - Develop/Demonstrate Seismic Retrofitting Techniques in Mid-America Highway Structures
Many existing bridges within areas affected by strong ground motions originating in the NMSZ were designed without seismic considerations. One recent assessment of four highway bridges in the vicinity of NMSZ indicated that the reinforced concrete (RC) piers of two of the bridges are likely to collapse under a strong earthquake due to insufficient flexural/shear strength in the cap beams. Furthermore, some of the unique construction approaches in the Mid-America areas lead to reinforcement details in beam-column or column-footing joints that are inadequate to transfer the shear force and moment from one component to another. The main purpose of this element is to assess existing retrofit methodologies, and develop and improve the advanced seismic retrofitting technology for bridges to enhance their performance during earthquakes, originating from the NMSZ. The focus of this element will be on the improvement and development of techniques suitable to the Mid-America area.

Element 7 - Exchange and Transfer Technology

The purpose of this element is to transfer the technology developed by this study to State bridge engineers and other practitioners.